1. Field of the Invention
This invention concerns measuring gages and more particularly measuring gages of the type in which opposed gaging fingers carrying gaging contacts are adapted to engage a workpiece to measure the dimension of the workpiece part disposed in contact with the gage contacts.
2. Description of the Prior Art
Opposed contact gaging devices are widely used for measurement of outside and inside dimensions of workpieces such as round shafts, tubing, etc. These devices include a pair of opposed gaging fingers which are adapted to be moved into and out of engagement with the workpiece, with a displacement transducing arrangement generally provided measuring the relative position of the opposed gaging fingers to thereby generate signals corresponding to the dimension of the workpiece disposed between the gaging contacts. Control of the gaging contacts, both into and out of engagement with the workpiece, is a critical aspect in the design of such gages, but particularly critical is the mode in which the opposed gaging fingers engage with the workpiece, since the accuracy of such gages is largely dependent on the uniformity of gaging pressure applied during measuring operations. Variations in deflection of the parts and the gage structure during the gaging operations would contribute greatly to the variations in readings obtained by such devices.
Another problem is encountered in the measurement of workpieces which are not properly centered within the gage, i.e., errors may arise if the parts are out-of-round or are bowed along their length, etc., since the opposed contacts usually move into engagement with the workpiece simultaneously, and if the workpiece is not centered one or the other contact would encounter one or the other surface of such workpiece first, arresting further movement inward and contributing to a false reading.
The convenience in use of such devices would also be greatly enhanced if a simplified control over both of the gaging fingers could be had with a single manipulation and which also provided for controlled movement inward, thus to avoid excessively sharp impacts with the workpiece in the case of spring bias or counterweighted movements.
Any such devices should, of course, if possible, be as simple as possible to minimize manufacturing costs and maintenance requirements, and to improve reliability.
Typical devices of the sort described are disclosed in U.S. Pat. Nos. 3,851,396, 3,781,997, and 3,802,087. All of these devices disclose measuring gages of this type which either require complex manipulations by the operator, and all involve excessively elaborate constructions which for the most part require the operator to separately manipulate each of the opposed gaging fingers, at least during set up operations.
It is, therefore, an object of the present invention to provide an opposed contact measuring gage which provides for carefully controlled and uniform application of a gaging pressure to a workpiece.
It is a further object of the present invention to provide an arrangement to compensate for a misaligned or otherwise off-center positioned workpiece.
It is yet another object of the present invention to provide an opposed contact measuring gage in which the opposed gaging fingers are manipulated by a single control device which is of very simple construction and which allows controlled movement of the gaging fingers both into and out of engagement of the workpiece and which furthermore allows positioning of the gaging contacts in any adjusted open position.
It is still another object of the present invention to provide a mechanism which allows automatic clutching and release of a rotary shaft with rotation of a control knob.